The present invention is related to an electronic metering apparatus for metering liquids.
Known electronic metering apparatuses for metering liquids have a drive with an electric motor and an electronic display device, respectively, and a displacer device driven by the motor, which comprises a cylinder with a plunger arranged movable therein. The displacer device can be communicatingly connected to a replaceable pipette point. By means of the displacer device, an air cushion is dislocated, which aspirates liquid into the pipette point and ejects it from the same, respectively. Pipette points and syringes are preferably disposable objects for single use, made from a plastic material. The stroke volume of the plunger does not exactly correspond to the picked-up and delivered liquid volume. This is particularly due to the fact that the air column becomes somewhat longer through the weight of the liquid, so that the stroke volume exceeds the liquid volume.
From WO 2005/079988 A1, the entire contents of which is incorporated herein by reference, a pipette with an electronic display and a calibration function is known. The calibration function includes the input of an actually pipetted volume at a certain displayed volume into the control system of the pipette via a user interface. The control system calculates calibration data and memorizes them in a memory. By means of the calibration data, the stroke length of the plunger or the volume displayed by the display device is corrected, so that the displayed volume corresponds better to the actually metered volume. It is possible to memorize different calibration data in the control system, which are used for different pipetting functions (also called “modes of operation”), like direct pipetting or reverse pipetting. Direct pipetting includes the direct pick-up of the desired volume to be delivered, whereas reverse pipetting includes the pick-up of a volume which is greater than the desired volume to be delivered, which is delivered thereafter.
In the known pipette, a new calibration may become necessary, when one of the provided modes of operation is not selected but other conditions of operation are changed instead.
Departing from this, the present invention is based on the objective to provide an electronic metering apparatus, the use of which under different modes of operation is less impaired by calibrations.